Lumpy running 2.25 petrol

[jordan_meakin]

Hi all,

I have today bought my first SWB 2.25 petrol. I have owned 4 series before but never with this engine. My other current landy is a 109 2.6 6 cylinder.

The new SWB runs pretty well but seems a little hesitant and spluttery on moving off/low revs. Does anyone have any ideas what it could be? I'm assuming it's fuel related but haven't investigated too much. Also, how much tappet noise should I expect from these engines? The 2.6 is pretty tappetty but not sure how much to expect from the 2.25.

Any help would be appreciated before I start taking carb off etc.

Thanks!

[Josh NZ]

Check the carb/manifold for air leaks by spraying wd40 around, if the engine revs up, you found one!

Sputtering could be fuel starvation which would mean pulling the carb to bits and checking the float levels. The Haynes manual is a great help on this, I had so many issues with my 2.25 not quite running right. Probably wouldn't hurt to drain the fuel pump sediment bowl, and change the fuel lines as they can gunge up which won't help.

If you have a zenith 361V Carb, Check timing by loosening the dizzy clamp (3 bolts) and then with the engine running, simply twist the dizzy one way or the other until the revs are at their highest. Once you find that point, turn the enginr off, tighten the bolts again and wind out the idle stopper screw.

The Haynes manual is really invaluable for doing these sorts of fixes. Also check that the fuel is fresh of its been sitting in the tank too long!

Let us know how you get on, a 2.25p running sweetly is one the best sounds out there (next to a V8!)

[Jamie_grieve]

I'd agree with what he said about the air leak to start with^^^^^^^^^^^

The 2.25 should be really quiet with no tappet sound at all almost. They are a very underrated engine just because they are a bit gutless for their size but it should not be unpleasant at low revs, they have more torque up to 1000 rpm than most modern engines the same size.

Do the basics if it's new to you, plugs, points, timing, fuel and start with air leaks and the idle screw at the bottom of the carb and make sure the advance is working in the distributer too.

As jjm248 said, a properly running 2.25 is a really sweet sound.

[secondjeremy]

Check the accelerator pump is actually working - take the air cleaner hose off the top of the carb and look down the hole while operating the throttle. You should see a strong jet of fuel go straight down the intake. I had to use parts from 3 Zeniths the other day before I got a working one.

Also worth checking the linkages and that the throttle opens fullt - not for the hesitation but general running.

[Team Idris]

It could be dirt in the valve work in the lid. I have little idea what it does, it's the only carb I've seen with it in, but dirt in it really held back a LWB S1 that was having trouble.

Even a bit flat it was waaay better than my S1 engine though. It's one of my favourite engines, being a petrol version of a diesel, so really strong in the block

[jordan_meakin]

Thanks everyone for your help. Will start looking today. Am I right that the mixture screw is on the bottom on the carb? And by the idle screw, the one sort of on the throttle linkage? Thanks once again

[Jamie_grieve]

Thanks everyone for your help. Will start looking today. Am I right that the mixture screw is on the bottom on the carb? And by the idle screw, the one sort of on the throttle linkage? Thanks once againThanks everyone for your help. Will start looking today. Am I right that the mixture screw is on the bottom on the carb? And by the idle screw, the one sort of on the throttle linkage? Thanks once again

Yes, sort of, the two screws are both for the idle, the top one is just the throttle stop screw and the bottom one is the idle mixture screw.

I'd firstly make sure the timing is right before trying to mess around with the carb. Someone was probably there before you. I don't know where you are or what kind of petrol you have but 6º BTDC is about right static timing. Engine switched off, turn with the starting handle or use the fan whilst tensioning the slack side of the belt until you get the timing marks where you want them then ignition on and turn the distributer opposite the wee arrow on the rotor arm until the points just open and you'll see and hear a spark. That's close enough for our purposes. this will work for petrol between 95 and 98 octane, you might have to compensate if you're in Jabrovia.

Onto the carb, turn the top screw behind the linkage back to drop the revs to as slow as it will go without cutting out.

Screw the idle mixture screw all the way in and the engine should stop, then back it out one or two turns and the engine should start and with the engine running adjust it to as high an idle as you can with the idle mixture screw then back the idle off with the top screw and repeat.

If everything's good you'l find a zone where turning the screw in or out drops the revs and that's where you want to be.

Hopefully you have a Zenith carb, those cheap Webbers people put on years ago were carp and cost horse power and supposedly saved fuel by making the whole thing run lean that meant you had to hammer them to go anywhere and use more fuel o do it.

If the idle mixture doesn't do anything at all the carb might have an internal leak or a worn throttle spindle.

Tell us how you go.

[Michele]

Hi all,

I have today bought my first SWB 2.25 petrol. I have owned 4 series before but never with this engine. My other current landy is a 109 2.6 6 cylinder.

I think I'll start a thread about this, but what how is the 2.6 6L in real life?

I heard mixed opinions, even about spares nobody agrees, some say nothing is available anymore, some say everything can be had off the shelf.

[Josh NZ]

In my opinion, the 2.6 is a nice engine. However, it's reputed to be troublesome in terms of burning out valves, overheating and being horrendously thirsty.

It has nice smooth power and torque delivery, and it does sound nice! Not sure about parts availability. I would've thought that if you can buy parts from something like a 1948-49 series 1 you could find some for the 2.6!

[Tanuki]

Check that the vacuum-advance diaphragm on the distributor is working: the transition from idle [when there's no vacuum applied to the dizzy] to just-off-closed-throttle [when you get lots of vacuum] can be messy if the diaphragm's failed and/or the connecting vacuum-pipes are blocked.

A good test: With the engine idling (let's say 800RPM) pull off the distributor vacuum-pipe from the carb. Engine revs should not change.

Now, suck *hard* on the pipe to the distributor. This will advance the ignition and if the vacuum-diaphragm is OK, the revs should rise noticeably (to at least 1000).

If you can't maintain suction on the pipe to the distributor, or if the RPM doesn't rise - you've got a blocked pipe, a perished diaphragm, or a seized dizzy base-plate.